Mechanics of
Movement
Part 3
ACTION COMING
Viewed from the front, the forelegs converge to the centerline of
the body, or single track. From the point of shoulder down, the line
of the leg should be straight. The straight line does not start at
the tip of the scapula, because the scapula and upper arm wrap
around the curvature of the chest which, unless the dog is
remarkably slab sided, should have some breadth (Fig 1). Twisting or
buckling of the elbow or pastern joints are serious faults, and may
forewarn serious injury if the dog attempts high level jumping.
Crossing over shows a marked lack of balance and wastes a lot of
energy, while moving wide will cause the dog’s weight to be shifted
back and forth laterally, another major waste of energy. Crabbing,
where both the forehand and the rearhand single track, but on
parallel lines, also wastes energy, and is driving energy along a
spine which is not aligned to the dog’s direction of travel (Fig 2).
Whatever energy is being dissipated laterally or in any direction
other than that which the animal is moving, is being wasted.


ACTION GOING
Viewed from the rear, the hind leg in the supporting position should
describe a virtually straight line. The muscles of the hind leg are
not designed to support a leg whose joints are buckling laterally,
and any tendency to cow or bandy hocks, knock or wide knees will put
a huge burden on the joints, and dissipate energy unnecessarily (Fig
3, Fig 4). However, the forward moving leg will probably not be
straight, as seen from the rear. A folded leg will show massive
muscles well bunched up, and this usually causes the leg to swing a
little wide, and out of the single tracking position. The dog whose
leg maintains the single track position at all times may be too
thinly muscled and narrow in body. Watch any athletic animal coming
towards you, and you will see that the swinging limbs leave the
centerline (Fig 5). Also visible going away is the firmness of the
back. Some animals may be well enough constructed, but are so poorly
conditioned that in motion one can see the back bouncing, flexing
laterally or rolling. Bad condition can be as detrimental to good
movement as bad structure (Fig 6).



SIDEGAITING
Sidegaiting at the trot gives a good profile of the dog's
conformation in movement. It demonstrates the drive in the rear, the
reach in front, and the strength of the back spanning the distance
between. The juncture between the lumbar and thoracic vertebrae is
what I call the true coupling between the drive train and the load
(Fig 7). The bulk of the dog’s body weight consists of the head,
neck, forehand and chest, all of which is suspended in some way from
the thoracic vertebrae. At this point along the spine, the dorsal
spines change from the forward thrust of the lumbar region, to the
taller, slightly backwards configuration of the withers. Between
these is a slight dip. This dip may or may not show, depending on
the dog’s muscling, fat coverage and coat quality, but it is there,
and it’s perfectly normal (Fig 8). All land mammals have it.
Breeding in a roach to try to eliminate it in some misguided attempt
to produce a stronger looking back actually produces a spine that
cannot as efficiently transmit power. The vertebral disks of the
withers should align in a straight line with the lumbar vertebrae,
to most efficiently continue the path of propulsive power, but the
visible silhouette of the correct back will show a slight change in
direction between the line of the withers and the back. As long as
there is no actual buckling of this coupling, the dog is showing a
normal back
.
During the power generating stage of the stride, energy travels up
from the ground, along each leg bone and is concentrated into the
hip joint. This joint must take every bit of force provided by the
rear, and channel it upward and forward into the spine. When you
realize the stresses the hip joint must tolerate, the deterioration
over time of less than good hips is easy to understand. Open a
normal joint of almost any mammal, and you will see a perfect
sphere, pearl-like in its smoothness, riding inside a similarly
flawless, satiny bed. The deeper and more perfect the joint, the
greater the surface area in that joint available to absorb the force
of the stride and distribute it evenly into the pelvis, and the less
stress applied to any particular point of the sphere. Inconsistency
over the surface of that sphere alters the distribution of force in
the same degree, decreasing it in some spots and increasing it in
others, eventually producing the flattening effect and other
arthritic changes seen in dysplastic hips. Anyone who has suffered
heel spur knows how uncomfortable even minute bone remodeling at a
pressure point can be.
From
the hip joint, energy is transmitted through the pelvis into the
sacral joint, where the spine and the pelvis are joined. The gentle,
moderate slope of the pelvis enables power to be guided gradually
into a horizontal direction, reducing stress on both the hip and
sacral joints (Fig 9). If the pelvis is very steep, as it is in so
many American show dogs, the sacral joint must absorb more energy
than it should. If it is very flat, the hips must absorb too much
energy (Fig 10). The degree of pelvic slope that we want in our
shepherds isn’t really any different from what is seen in almost any
four legged beast who must carry its own weight and still move
quickly and efficiently. The crocodile, which rarely supports its
weight off the ground and is an inefficient mover, has a pelvis
whose angle is almost completely level. On the other hand the
elephant, that must support a huge amount of weight almost every
hour of its life and cannot move faster than a running walk, shows a
pelvis that is almost completely vertical. Most others; felines,
canines, ungulates of all kinds; show a moderately sloping pelvis.


Stride
length can also be affected by pelvic slope because of the
alteration in the leverage of the muscles. In a steep pelvis, the
muscles attaching the rear of the pelvis to the femur are shortened,
reducing thrust. In a flat pelvis, the muscles attaching the front
of the pelvis to the femur are shortened, reducing forward reach.
Either way, reach and follow-through are similarly affected, stride
length is compromised and power reduced (Fig 11).
From the rearquarters, power is
transmitted forward through the lumbar vertebrae. These are thick,
massive disks that can absorb large amounts of energy, and to whose
long, forward pointing processes are anchored the muscles that help
pull the leg forward and arch the spine. The lumbar vertebrae must
also support the weight of the dog’s entire front half when
suspended. In motion, the lumbar spine should be straight and
horizontal for the energy it must carry to transmit without wastage.
If it is sagging, energy will be dissipated in directions other than
forward, and the spine’s ability to absorb a powerful rear thrust
will be compromised (Fig 12). Similarly, if the area is roached,
buckling and energy wastage will also occur. The greater the force
applied, the greater will be the tendency to buckle, increasing
vulnerability to injury. Animals with even a slight tendency to a
roach back when standing will usually show an even more pronounced
roach in motion, and this is why.


Weak withers are as reprehensible as
a weak back. The area of the withers and neck is cloaked with the
massive muscling required to move the entire fore assembly, rotating
the scapula forwards and backwards, and absorbing the impact of the
forehand stride. In the rear, the solid, bony mass of the hip joints
and pelvis absorb the stride, but in the front there is only the
saddle of muscle over the withers. Weak withers will show in the
dog’s inability to reach well ahead, and in a jolting action of the
tip of the scapula under the skin (Fig 13). This can be subtle at
the trot, but when jumping, the shoulder blades almost seem to drive
themselves out the dog’s back. Strong, high withers with a muscled,
well carried neck showing an elegant arch are indicative of a
powerful forehand, and without them even ideal shoulder angulation
won’t be as effectively utilized.

Of course, a firm back doesn’t mean that the spine cannot flex.
Flexing is most obvious at the gallop, when the spine itself becomes
a instrument of propulsion, particularly through the lumbar region,
gathering energy and propelling the body like a spring with each
stride. Even at the trot, it may show a tiny bit of flexion at each
stride, adding a bit more forward propulsion. A strong back needn’t
look like a steel post without any flexibility at all (Fig 14).
Despite its flexibility, the spine must remain level. Animals who
run “downhill” with their withers lower than their croups are
usually much less angulated in the rear than in the front, and are
completely unbalanced. Some of their forward energy is being wasted
downwards, throwing too much stress on the forehand (Fig 15). Dogs
that run uphill have the reverse problem, wasting energy upwards,
thrusting the front too high and stressing the rear (Fig 16).


As the dog moves ahead, its power both in the front and in the rear
is coming from muscular exertion, tendon elasticity and the pull of
gravity. The latter is the pendulum action of the the body literally
falling forward from its own weight and inertia over the forehand,
and is a source of “free” energy. The higher a body is off the
ground, the greater the pendulum action achieved. Giraffes use a lot
of it. Dachshunds use very little. The longer the legs, the more of
this free energy is available to the animal, another argument
against very low stationed, short legged dogs.
Anyone who has looked closely at a
good moving dog will have noticed that it doesn’t literally single
track. To achieve single tracking, the feet not only have to
converge on the centerline of the body, the rear feet have to step
into the tracks left by the front feet. Unless an animal is square
in structure with very little angulation, like elephants or fox
terriers, there will be some degree of overreach, with the rear feet
landing ahead of the step of the front feet. That means that the the
rear foot as it travels ahead must move to one side or the other of
the front foot to clear it. The front foot does not move ahead of
the rear foot, if the dog is coordinated and moving in proper
rhythm. When the rear leg is at maximum extension forward, the front
foot will be close to its maximum rearward follow-through, and the
two must cross each other, as seen from the side.
A coordinated dog will show a left or
right lead at the trot, with one hind foot passing on the inside and
the other passing on the outside of the forefeet. If the dog is
moving to the right, it will have a left lead, with the left rear
foot passing on the outside. If it is moving to the left, it will
have a right lead, with the right rear foot passing on the outside.
This results in triple tracking and helps the dog direct its energy
and make the turn. In nature, animals rarely move in perfectly
straight lines (Fig 17, Fig 18).


Occasionally there seems to arise a
debate on whether the supported trot or flying trot is the more
correct gait for the breed. In fact, both are typical. The supported
trot is a two-beat gait, executed at lower speeds (Fig 19). The
flying trot is a four beat gait and a function of higher speed (Fig
20). This is because, when the diagonal legs of an ideally
constructed animal with absolutely balanced angulation are moving in
perfect cadence and are at full and equal forward extension, the
rear foot will be at a slightly lower level than the fore foot, and
will strike the ground fractionally ahead of it. This is not without
purpose, as it is the hind foot that finds the dog’s centre of
gravity and enables it, if necessary, to adjust its balance before
propelling its weight over the foreleg. Unbalanced dogs may show a
tendency to touch down much earlier in the rear than the front, as
they are trying harder to achieve equilibrium, while balanced but
under angulated dogs, as well as correct dogs moving at a slow jog
trot, will exhibit the simple two-beat trot.


The correct dog is the one that can cover the greatest amount of
ground with the least expenditure of energy. Assuming dogs of equal
size, condition, age and temperament, it is obvious that the flying
trotter will cover more ground. The flying trotter's stride is equal
to the supported trotter's stride plus the length of its period of
suspension. The issue is whether the flying trotter is expending
more effort than the supported trotter and, if so, whether the
difference is more or less than the effort the supported trotter
would have to expend to achieve equal ground coverage. This can be
determined by observing when the dog shifts its gait in the attempt
to minimize its expenditure of energy: the stage in its movement
when the dog shifts up to a flying trot.
The
flying trot is a function of speed and there is likely no dog of any
breed that is not capable of it (Fig 21). The flying trot is not a
trained or handler induced gait. All dogs can do it, no matter their
structure, good or bad. The flying trot is nothing more than a
faster version of the supported trot, just as the suspended gallop
is a faster version of the canter. In nature, the only real
impediment to moving with suspension is body size and weight -
extremely large animals cannot achieve a period of suspension, or do
so rarely and with great effort.
The dog at the walk, when it wants to
increase its speed or the amount of ground it covers, increases both
the length and speed of its strides, no differently than humans.
Anyone who has ever tried power walking, the human equivalent of the
supported trot, will realize that at some point the walking gait
demands a great deal of energy and it becomes easier to maintain or
increase speed by shifting into a run, or flying trot, and utilizing
the inertia of the body’s motion through space. The poorly angulated
dog cannot achieve a long length of stride and must attempt to
achieve greater speed by moving faster, and ultimately shifting into
the next higher gait earlier than would the correct animal. The
better structured animal can stretch out into a near maximum length
of stride at the supported trot, while the inferior dog must shift
into a flying trot to keep up. In other words, a period of
suspension at a relatively low rate of speed is probably indicative
of structural problems. Increased demands for speed will eventually
cause the ideal dog to shift into a fast flying trot as well, but at
the same time its inferior mate will have to resort to a canter or
gallop, giving the trotter that beautiful illusion of moving in slow
motion.
Breeders
must be careful, however, not to develop the flying trot into a
caricature of itself, producing animals that are loosely ligamented
and over-angulated in the rear, and that show a length of stride
that, while impressive to the uninformed, is excessive (Fig 22).
This extreme type loses its athleticism at other gaits and in
jumping. The correct GSD is capable of a supported trot that is
longer, more flowing and more efficient than any other breed, but it
can also display the most efficient and spectacular version of the
flying trot (Fig 23).
